docs: def compand(self, attack=0.2, decay=1, soft_knee=2.0, threshold=-20, db_from=-20.0, db_to=-20.0):
          """compand takes 6 parameters: 
          
          attack (seconds), decay (seconds), soft_knee (ex. 6 results 
          in 6:1 compression ratio), threshold (a negative value
          in dB), the level below which the signal will NOT be companded
          (a negative value in dB), the level above which the signal will
          NOT be companded (a negative value in dB). This effect
          manipulates dynamic range of the input file.
          """
          self.command.append('compand')
          self.command.append(str(attack) + ',' + str(decay))
          self.command.append(str(soft_knee) + ':' + str(threshold) + ',' + str(db_from) + ',' + str(db_to))
          return self